Which blood types can donate to which? This free blood type compatibility calculator checks any donor-recipient pair against standard ABO and Rh compatibility rules for red blood cell donation.
This reflects standard red blood cell donation compatibility rules. Actual transfusion decisions are always made by medical professionals with full cross-matching.
How the Blood Type Compatibility Calculator Works
This tool checks a chosen donor blood type against a chosen recipient blood type using the standard ABO and Rh rules that govern red blood cell compatibility. It is a general educational reference, not a substitute for the lab cross-matching that real donations and transfusions always require.
Formula: Each blood type has a fixed list of recipient types it can safely donate red blood cells to, based on standard ABO/Rh rules: O- can give to all 8 types (the universal donor), O+ can give to O+, A+, B+, and AB+, A- can give to A-, A+, AB-, and AB+, A+ can give to A+ and AB+, B- can give to B-, B+, AB-, and AB+, B+ can give to B+ and AB+, AB- can give to AB- and AB+, and AB+ can only give to AB+ (the universal recipient). The calculator checks whether the chosen recipient type appears on the chosen donor’s list.
- Donor blood type — the blood type of the person giving blood, chosen from O-, O+, A-, A+, B-, B+, AB-, or AB+
- Recipient blood type — the blood type of the person receiving blood, chosen from the same eight types
Example Scenarios
| Donor Type | Recipient Type | Result |
|---|---|---|
| O- | AB+ | Compatible |
| O+ | A- | Not Compatible |
| A- | AB+ | Compatible |
| B+ | O+ | Not Compatible |
| AB- | AB+ | Compatible |
| A+ | B+ | Not Compatible |
Blood Type Compatibility Calculator FAQ
Why is O- called the universal donor?
O- red blood cells carry neither A nor B antigens nor the Rh(D) antigen, so they are compatible with all eight blood types under standard ABO/Rh rules. That is why O- appears as a match for every recipient type in this calculator.Why can AB+ only receive from certain donor types in this tool, if AB+ is the universal recipient?
AB+ is the universal recipient, meaning every donor type can give to an AB+ recipient — but that is different from asking who AB+ itself can donate to. As a donor, AB+ blood carries both A and B antigens plus Rh(D), so it can only be given safely to other AB+ recipients.Can an Rh-positive donor give blood to an Rh-negative recipient?
Under standard Rh rules, no — Rh-positive blood is generally considered unsuitable for Rh-negative recipients because it can trigger an immune response. Rh-negative donors, by contrast, can give to both Rh-negative and Rh-positive recipients of the same ABO group.Does this calculator replace the cross-matching done before a real transfusion?
No. This tool only reflects the general ABO/Rh compatibility rules for educational purposes. Real transfusions always require laboratory cross-matching and screening by qualified medical professionals before blood is given to a patient.Can this calculator be used to determine a child’s possible blood type from parents?
No. This tool is built specifically for donor-to-recipient transfusion compatibility, not for genetic inheritance calculations. Blood type inheritance follows separate genetics rules and should not be inferred from this donation-compatibility tool.Why does my donor and recipient pair show Not Compatible even though both are common blood types?
Compatibility depends on whether the recipient’s blood type appears on the specific donor type’s approved list under ABO/Rh rules, not just on how common either type is. Many otherwise ordinary pairings are still incompatible because of antigen mismatches.Related Calculators
If you found this useful, other blood-related tools include the blood pressure tracker for logging readings over time, the blood sugar level checker, and the anemia risk calculator for a general look at iron-related risk factors.